Nuclear haze: Will new builds take us into the financial unknown again?

But while the industry has tried to clean up its act, and become more transparent and efficient, old habits die hard. Billions of pounds of taxpayers' money have been spent, and wasted - for example, when British Energy was privatised and then had to be bailed out by the Government to avoid going into administration. Billions more (at least £60bn at the last count) will be needed to clean up the radioactive waste created by the industry.

Because of the secretive nature of the nuclear sector, it is hard to analyse its historical financial performance, but whether it has ever made a real profit must be extremely doubtful. The point is a timely one, for at the CBI conference on Tuesday, Tony Blair is set to announce the terms of the energy review, which is expected to pave the way for a new generation of nuclear reactors. These, we are told, will be better, cleaner - and profitable.

So before the Government sets about creating a new breed, what are the costs and benefits of nuclear power to date - and how can we be sure the mistakes of the past will not be repeated?

The UK civil nuclear industry was born out of the arms race at the start of the Cold War. Sellafield, the sprawling site in Cumbria that hosts the Thorp fuel reprocessing factory, was originally owned by the Ministry of Defence.

In the early days, the industry was chaotic, experimental and, since it was (until the mid 1990s) entirely state-owned, the attitude seemed to be that costs were largely incidental.

Many mistakes were made. The biggest was choosing to reprocess spent nuclear fuel - the idea being to use the plutonium and uranium again rather than rely on scarce and expensive imports. The plutonium also had military uses.

The first reactors, the Magnox fleet, were designed specifically with fuel reprocessing in mind, as were the next generation, the AGRs. This added to the cost and complexity.

The Thorp reprocessing plant, which cost £1.8bn to build, was closed in April this year after the discovery of a major leak and may never reopen.

Thorp was never efficient anyway, as it was not able to separate all the radioactive waste from the depleted uranium it produced. It became far easier and cheaper for generators to import uranium, the price of which fell as new reserves were found - undercutting the whole rationale for reprocessing.

Another facility, the Mox plant, was built in 2001 to take the reprocessed fuel from Thorp and produce new fuel, but it has won few contracts. Critics who said at the time it was not economic appear vindicated.

The Nuclear Decommissioning Authority, which has inherited the public sector nuclear liabilities, says it is discussing with the Government whether to treat unused, reprocessed plutonium (an estimated 75 tons is in storage at Thorp) as an asset or a liability. If, as is likely, it is the latter, disposing of it will add billions more to the NDA's estimated liabilities, set at £56bn (excluding those of British Energy).

British Nuclear Fuels (BNFL), which remains state-owned, was formed in 1971. It inherited the generation, reprocessing and manufacturing activities from the UK Atomic Energy Authority. BNFL's accounts for the 1980s give the balance of its retained profits and reserves, but little clue as to how much money it received from government, and how it was spent. The late Dr Mike Sadnicki, an academic at Sussex University, produced, in 2002, a forensic analysis of BNFL's historical financial performance. It painted a picture of underestimated liabilities, inefficiency and government subsidy via various departments and other state-owned utilities.

He found that BNFL's cash position was enhanced in the 1980s and 1990s because it was the sole reprocessor in the UK, providing services for British Energy, its forerunners and BNFL's generating subsidiary, Magnox Electric. (Indeed, British Energy's near collapse was in large part due to its uneconomic but compulsory reprocessing deals with BNFL.)

BNFL's contracts with UK generating utilities were always agreed on a cost-plus basis, so any budget overrun - a frequent event in the UK nuclear industry - was borne by the customer, not BNFL.

The group was also given a remarkably free rein by government and regulators. John Wakeham, a former energy secretary, said in 1990: "BNFL's directors are responsible for its management on a day-to-day basis. This includes the financial management of the company and its internal systems. I have no responsibility for these matters."

Even a decade later, good financial housekeeping had apparently not taken hold. The former chairman of BNFL, Hugh Collum, who died earlier this year, was quoted as saying in 2000, when he took over: "There is nobody at board level with proper plc experience ... This company is not good at forecasting and not good at estimating." His comments followed the scandal a year earlier when BNFL staff were found to have fiddled data on a shipment of Mox fuel to Japan.

There was no way of knowing how economic nuclear generation was compared to coal- and gas-fired power stations because the CEGB, responsible for supplying electricity until privatisation in the 1990s, did not split out the costs of generation.

In the 1990s, as the Government looked to privatise the nuclear industry, attempts were made to produce more open accounts. Some were laughable. The interim results statement from Nuclear Electric in 1992, for example, consisted of three brief pages of information. The more government officials looked into the industry's accounts - and liabilities - the more shocked they became. Only the eight most modern reactors were deemed suitable for privatising.

The float price of British Energy, £1.5bn, was around half what it cost to build its most modern reactor, Sizewell B. Its obligation to pay only £17m per year for its estimated £5bn clean-up bill was the product of a flawed short-term fix to get the privatisation away in 1996 - another major factor in British Energy's near-collapse in 2002.

It is highly unlikely that reprocessing will form part of any new nuclear building programme. Nor will new reactors be of British design - for good reason. While nuclear power has consistently provided around a fifth of the UK's electricity, the extent of the waste - both radioactive and financial - will never be known.

A report by the Committee on Radioactive Waste Management will propose how to deal with the nuclear waste - probably by building an underground repository at a cost of around £8bn. If the Government acts on this report, this will help get rid of at least some of the uncertainty. However, nuclear energy consultant John Large says: "You won't know for sure for another 100 years if there's been a slow leak somewhere."

The nuclear industry says next time it will be different. It had better be.

FIFTY YEARS OF LIVING DANGEROUSLY

1954: the United Kingdom Atomic Energy Authority (UKAEA) was established and given responsibility for virtually all aspects of the developing UK nuclear industry.

1956: the UK became the first country in the world to adopt nuclear power on an industrial and commercial scale when Calder Hall, a Magnox prototype, was commissioned by the UKAEA.

1957: fire at Windscale, a nuclear complex near Calder Hall. In 1982, a report was issued suggesting that 32 deaths and 260 cases of cancer were attributable to radiation leaked. The UKAEA changed the complex's name to Sellafield.

1964: the Government decided to develop Advanced Gas Cooler Reactor (AGR) technology to succeed Magnox. In all, seven of these reactors were built in the 1970s and 1980s.